The present invention relates to a system for replenishing a fresh developer to a developing device of an image forming apparatus and collecting a used developer, and a developer cartridge for such a system.
A copier, facsimile apparatus, laser printer or similar electrophotographic image forming apparatus includes a developing device which stores a developer and develops an electrostatic latent image formed on a photoconductive drum or similar image carrier with the developer. As the developing device repeats development, a toner contained in the developer is sequentially consumed with the result that the toner concentration of the developer becomes too low to form desired images. Therefore, it has been customary to provide the developing device with a developer replenishing device for replenishing a fresh developer in matching relation to the decreasing toner concentration. One of modern developer replenishing devices uses a developer cartridge, or toner cartridge as generally referred to, containing only a toner, i.e., one-component developer or a toner and carrier mixture, i.e., two-component developer.
It has also been customary to provide the developing device with a device for collecting a toner removed from the image carrier together with various impurities and discarding them. Usually, this collecting device is implemented as a container physically separate from the above-stated developer cartridge. This kind of configuration has a drawback that the overall size of the developing device increases. Moreover, when the developer cartridge and the container for collection are erroneously replaced, the developer flows out of the cartridge and contaminates surroundings.
To eliminate the above problems, Japanese Patent Laid-Open Publication No. 56-146171 discloses a photoconductive drum provided with a fresh toner container and a collected toner container which are formed integrally with each other with the intermediary of a partition. With this drum, it is possible to replenish a fresh toner and collect a used or waste toner automatically. In addition, the supply of a fresh toner and the disposal of a waste toner are effected at the same time when the drum is replaced, reducing maintenance work. This kind of approach, however, brings about another problem that the drum has to be replaced every time the toner is replaced, and the replacement of the drum is apt to damage the drum.
Japanese Patent Laid-Open Publication No. 2-33169 teaches a toner cartridge having a fresh toner compartment and a collected toner compartment separated from each other by a partition. The partition is formed with an opening in an upper portion thereof. A valve is provided in the opening and allows a toner to pass therethrough only from the collected toner compartment to the fresh toner compartment. Japanese Patent Laid-Open Publication No. 62-84049 proposes a toner cartridge having a fresh toner container and a waste toner container which are joined together by a separable member. Further, U.S. Pat. No. 4,744,493 discloses a toner container having a spiral configuration.
Other devices for toner collection are taught in Japanese Patent Laid-Open Publication Nos. 60-10274, 61-2172, 61-2173, 63-298370, 60-146265, and 61-9666. However, with such conventional devices, it is necessary to replace a container or tank for collecting the waste developer, including the toner, periodically, resulting in troublesome .operation. To reduce the frequency of such periodic replacement, the container or tank itself has to be provided with a large capacity, increasing the overall size of the developing device. Moreover, when the developer is to be collected in the container or tank, the toner contained therein is scattered around to contaminate the interior of the developing device.
The troublesome replacement of the developer cartridge and the container or tank for collecting the used developer will be obviated if the developer used and then collected is recirculated for reuse. However, practical schemes for implementing the recirculation have not been reported yet.